Perce,

I'm replacing the indoor section of the plumbing that feeds our
sprinkler system. The old PVC threaded fittings screwed in far enough
that the shoulder of the fitting contacted the body of the vacuum
breaker, but the new fittings bottom in the VB with more than 1/2 in.
of thread still showing. Would it be a good idea to cut enough off the
threaded portion of the PVC fittings so that none of the threaded part
(which I assume is the weakest part) is unsupported by the body of the
VB?

Having exposed thread won't cause any problems, in fact that's how most
threaded fittings end up.

If the vacuum breaker is heavy enough that you're worried about it, it
would be smarter to install some kind of strap to carry the weight of the
VB.

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com